Ideogram of human chromosome 1 ( HSA 1) and its orthologues as determined by E-painting in rat, mouse, dog, cow, opossum and chicken. The human chromosome coordinates of the breakpoint intervals are given to the right of the human ideogram in Mb. The chromosome number of the orthologous segments in the analyzed species is indicated to the right of each conserved segment. Chromosomal breakpoints have been evenly spaced in order to optimize visualization of the conserved syntenic segments. The resulting ideograms of the chromosomes and conserved segments are therefore not drawn to scale. The centromeric region is indicated by a black horizontal bar on the human ideogram. The stippled red lines indicate breaks present in all analyzed non-human genomes and which may thus be attributable to rearrangements specific to the primate lineage (see Table 3). Black lines within the ideograms indicate breaks within the contiguous sequence that probably resulted from intrachromosomal rearrangements caused by inversions. Stippled green lines indicate the positions of 'reused breakpoints', defined as locations in which breakpoints were found to map to the same genomic intervals in at least three species from two different clades. The complete set of E-painting results for chromosomes 1–22 is given in Additional file 1. un: undetermined.